1. Field of the Invention
The present invention relates to a reaction cuvette for an automatic analyzer for measuring a concentration of a test article in a sample, a method of surface treatment for a reaction cuvette for an automatic analyzer, and an automatic analyzer having the cuvette.
2. Description of the Related Art
One of the problems in the field of automatic analyzers is reduction of amounts of samples and regents used.
With the tendency for increase of analytical items, an amount of samples used for each discrete analytical item becomes smaller and analysis of a minute amount of samples is generally performed as a routine work.
Also reduction of amounts of samples and regents used is required in terms of reagent cost and their disposed amounts.
A new problem has occurred that has not been experienced to satisfy the need for such reduction.
Even in the conventional technology, there is the possibility that air bubbles generated by agitation or the like and adhered on an inner wall of a reaction cuvette interfere with an optical axis of a light beam passing through the reaction cuvette because of a downsized reaction cuvette.
Especially, the air bubbles adhered at four corners of a bottom portion of the reaction cuvette may not easily be removed because the air bubbles are supported by two wall surfaces and the bottom surface. When air bubbles are generated, an incoming light beam is scattered by the air bubbles adhered on the reaction cuvette and the degree of scattering cannot be ignored.
Furthermore, there is another necessity of reducing an amount of water used for cleaning the reaction cuvette and remaining still in the reaction cuvette even after cleaning in association with reduction of an amount of a reagent liquid used in testing.
There has been proposed a method of making inner wall of a reaction cuvette hydrophilic to overcome the problems described above. Effective methods for making resin surface hydrophilic include the oxygen plasma treatment, ozone treatment, ozone water treatment, and corona discharge treatment.
In relation to the technical tendency described above, there has been examined the possibility of making inner walls of a reaction cuvette hydrophilic with ozone water. As disclosed in JP-A-2005-77263, if ozone water which is a liquid is used, the entire surfaces of a reaction cuvette can be made hydrophilic, and thereby air bubbles are prevented from adhering to inner walls and a bottom portion of the reaction cuvette.
With the technique, however, a resin is oxidized excessively, and the translucency becomes disadvantageously low. In an automatic analyzer, when optical absorbance of a reaction cuvette itself increases, a period in which the reaction cuvette can be used becomes disadvantageously short.
Furthermore, it is difficult to maintain a concentration of ozone water at a constant level, and complicated processes such as cleaning and drying are required after completion of the treatment.
When the entire are of inner walls of a reaction cuvette is made hydrophilic, another problem may occur that a reagent inside a reaction cuvette moves over a surface of the reaction cuvette into an adjoining one to cause mutual contamination and provide abnormal analytical results.
An extremely difficult work is required to contact ozone water with only desired areas for hydrophilic treatment.
JP-A-2006-125897 discloses a method of partially improving wettability. Specifically, this document proposes treatment with ozone water requiring masking with a complicated form for improving wettability of only a surface used on optical measurement on inner walls of a reaction cuvette.
There has also been examined the possibility of making inner walls of a reaction cuvette by spraying a gas containing ozone thereto.